1. Field of the Invention
The present invention relates to a multilevel wiring substrate used to mount a semiconductor multi-chip module, a semiconductor device using the multilevel wiring substrate, and a method of making the multilevel wiring substrate.
2. Description of the Related Art
In recent years, LSIs each having a high integration density and high speed have been developed as the rapid progress of the semiconductor technique when a computer or communication equipment is to be constituted by these high-performance LSIs, the mounting delay of signals transmitted between the LSIs causes the system performance having the LSIs to limit.
As a means for solving the above problem, an MCM (Multi Chip Module) in which bare-chip LSIs are mounted at a high density has been popularly developed. The MCMs are classified, depending on the types of substrates used in the MCMs, into an MCM-L in which bare chips are directly mounted on a printed board, an MCM-C which uses a ceramic substrate obtained such that ceramic thin films called green sheets are stacked and then sintered, and an MCM-D which uses a thin film multilevel wiring substrate. Of these types, the MCM-D is attractive due to its electrical characteristics, wiring density, and the like.
In the MCM-D, a base substrate serving as a base is required for forming a thin film multilevel wiring layer. A silicon wafer, a metal plate consisting of aluminum or the like, or a ceramic substrate consisting of alumina, aluminum nitride, or the like is used as the base substrate. When the ceramic substrate is used as the base substrate, a wiring layer can be formed inside the base substrate, and the base substrate can also be used as a package, thereby increasing a mounting density.
The base substrate using the ceramic substrate is conventionally used in a high-end field as of a super computer, where the high cost of the base substrate is permitted. However, when this technique is applied to a workstation or a personal computer, various types of base substrates must be made within a short period of time, and the cost must be decreased.
In a base substrate used in a conventional MCM, a wiring conductive pattern, an insulating layer, and via holes must be formed for each layer. Since this process is sequential, it takes a long time to complete the base substrate, and it is difficult to reduce the cost.